R=120;
C=33e-12;
TAY=R*C;
T=TAY/100;
t=0:T:(3*TAY);
N=length(t);
U(1)=0;
E=1;
for k=2:N
    U(k)=U(k-1)-(T/TAY)*U(k-1)+E*T/TAY;
end;
plot(t,U)